Pulmonary artery pressure--flow plots in hyperoxic and in hypoxic dogs: effects of prostaglandin E1.

The effects of prostaglandin E1 on mean pulmonary artery pressure (Ppa):cardiac index (Q) relationships were investigated in eight anaesthetized dogs, ventilated in hyperoxia (fraction of inspired oxygen (FiO2) 0.4) and in hypoxia (FiO2 0.1). Cardiac output was increased by opening an arterio-venous femoral bypass or reduced by stepwise inflations of a balloon in the inferior vena cava. Five-point Ppa:Q relationships were found to be linear in all experimental conditions. Hypoxia increased Ppa over the entire range of Q studied (1-5l.min-1.m-2). Prostaglandin E1 0.4 microgram.kg-1.min-1 intravenously decreased hyperoxic Ppa for Q ranging from 3-5 l.min-1.m-2, hypoxic Ppa for Q ranging from 2-5 l.min-1.m-2 and attenuated hypoxia-induced increases in Ppa. These results show that prostaglandin E1 is a pulmonary vasodilator in both hyperoxic and hypoxic conditions. At the dose of 0.4 microgram.kg-1, prostaglandin E1 partially inhibits hypoxic pulmonary vasoconstriction.